There is a demand to find new solvents to replace chlorofluorocarbons (CFC's) and hydrochlorofluorocarbons (HCFC's). These solvents typically have been used in a wide variety of applications including cleaning and degreasing solvents for the metal, textile and electronic industries, as flame retardants and heat transfer mediums for refrigeration processes. In recent years use of these solvents has been restricted because of concern over environmental hazards, particularly in light of the link between use of these solvents and the destruction of the atmospheric ozone layer. Highly fluorinated hydrofluorocarbons (HFC's) are considered to be viable alternatives for CFC's and HCFC's in many applications. The HFC's are chemically stable, nontoxic, nonflammable and less hazardous to the environment then either CFC's or HCFC's. However. HFC's are not considered to be as effective cleaning and degreasing solvents as the CFC's and HCFC's. Highly fluorinated hydrocarbons (HFC's) have a low solvating ability when compared with CFC's and HCFC's, and HFC's are not as efficacious as CFC's and HCFC's for dissolving greases and oils or disbursing other undesirable materials such as flux and flux residues on printed circuit boards. It has been determined that HFC's can be combined with other organic solvents to provide a cleaning solution having higher solvating ability. The added organic solvent must be carefully selected so the resulting cleaning and degreasing solvent maintains its desirable physical and chemical properties such as low toxicity, low boiling, environmentally friendly and nonflammable. Furthermore while a particular solvent mixture initially may provide the desired physical and chemical characteristics in bulk, i.e. non-toxic, low boiling, nonflammable and high solvating ability, in practice, the mixture may be inadequate.
Most solvent mixtures partition during use, especially when the solvent is heated during the cleaning process or during solvent recovery. Partitioning of the mixture provides a solvent that is deficient in one or more of its constituents. The resulting solvent does not have the same properties as the original solvent. For example, solvents are often heated to boiling to vaporize the solvent composition in a vapor defluxing or degreasing system. The vaporized solvent condenses on components such as circuit boards that are inserted into the system. When partitioning occurs, the composition of the vaporized solvent differs from the liquid solvent in the solvent reservoir. Partitioning results in a solution that can detrimentally affect the safety and efficacy of the cleaning operation. It is advantageous to provide non-partitioning solvents to ensure safe and effective cleaning and degreasing processes.
It is also advantageous to minimize partitioning during solvent recovery to improve efficiency and decrease costs. Solvents are often recovered by distilling used or contaminated solutions to provide essentially pure solvents that can be reused. Partitioning during recovery requires that one or more of the original components be added to the recovered solvent to maintain the original solvent composition.